Why Your Muscles Get Sore (And What You Can Do About It)

When you're struggling to walk down the stairs the day after a tough workout, should you view your soreness as proof you worked hard, or as a sign you overdid it? The truth is somewhere in between. Let's learn about where soreness comes from and how to keep it from making you miserable.

What Soreness Is

That next-day soreness isn't from lactic acid or any toxins produced during exercise. Think about it: if it were, the soreness would start at the gym and resolve over time. Instead, it's called delayed-onset muscle soreness (or DOMS) because it begins several hours after, and peaks (on average) around two days after exercise.

Exactly how DOMS develops isn't as well understood as you'd think, but exercise scientists agree that people who are experiencing soreness are also experiencing muscle damage and rebuilding. Proteins leave the injured cells while fluid and white blood cells rush to the rescue. As time goes on, the muscle cells are patched up and new cells are born, and all of them get stuffed with contractile proteins. Some or all of this response is probably involved in making us sore.

What Causes It

Almost any kind of hard exercise can result in soreness, especially if the exercises are new to you. We don't know why, but somebody who's in great shape can still be sore after an unusual workout (say, trying a new sport) and somebody who is used to their routine may avoid soreness even if their workouts are killer.

Some types of exercise are more likely to trigger it, though. The most notorious are eccentric exercises, ones where a muscle has to contract as it's lengthening. Think about the part of a bicep curl where you're lowering the weight; that's a textbook example of eccentric exercise, since the bicep is working (to slow the weight down) as it is lengthening. Another classic is downhill running, or walking down stairs. (Pro tip: if you're running stadium or skyscraper stairs for the first time, run up but look for an elevator to take back down.)

Stretching can also cause soreness, especially if the stretching is extreme. That's probably because the stretching damages muscle fibres. Static stretching and ballistic (bouncing) stretching can both do that damage. If you want to improve flexibility without pain, gentle static stretching or dynamic stretching is probably a better bet.

When It's A Good Thing

Soreness correlates pretty well with muscle growth, repair and recovery, so in a sense it's a sign of good things happening. If you live the gym rat life, or the active outdoor life, you're going to be sore at least some of the time and it's really OK.

You don't want to be sore all of the time, or severely sore, but more about that below.

When It's A Bad Thing

DOMS's dirty secret is that it comes with a loss of strength. It's not just that you don't feel like exercising. When you're sore, your muscles can't produce as much force. That weakness may last longer than the soreness, for days or even, in severe cases, weeks. If you're sore all the time, you may be sabotaging your own workout efforts because you're not working as hard as you could.

Since soreness and muscle damage go hand-in-hand, severe muscle damage that threatens your health, called rhabdomyolysis, will show up as severe soreness. If you ever wake up so sore you can barely move, and your muscles are swollen, and you're peeing brown, get to a hospital right away. Rhabdo can happen to athletes who engage in very long and tough workouts (or 100-mile endurance runs), feel like the tougher the workout the better, and are just mentally determined enough and just dumb enough to not stop when a workout is getting out of hand. (It can also happen to athletes who trust their coaches, when their coaches have those same qualities.) If this paragraph is terrifying you, and you're wondering whether your half-hour at the gym this afternoon might put you into rhabdo, relax. You're not in the at-risk group.

What You Can (And Can't) Do About It

When you're sore, you want to do something about it, right? Sadly, most of the things people do to try to relieve soreness don't usually help.

Massagemay help, but it's not clear what kind of massage is best or when you should have it. While we wait for more science to roll in, use it if it feels good.

Ibuprofen reduces inflammation, and large amounts can make you less sore. But ibuprofen also interferes with muscle growth, so popping "Vitamin I" probably isn't worth it. (Low doses won't do any damage, but they also aren't likely to help with pain either.)

Arnica (sold as under-the-tongue homeopathic pills with no actual arnica content, or as a gel) justdoesn'twork. Don't fall for it.

Most of the time, your best bet is to just wait. It's OK to go to your next workout, but take it easy. As long as you don't make it worse, the soreness will subside in a few days. Sleeping and eating well are never a bad idea, and the techniques above are fine to use if they make you feel better. So yes, maybe you overdid it just a little. But you can also be proud that you're getting stronger.